The present invention relates to a flow control valve for a hydraulic line.
Flow control valves which are connected to hydraulic lines control the throughflow of hydraulic fluid through the hydraulic line, the control behavior of the flow control valve being more or less independent of the viscosity of the hydraulic fluid and of the prevailing pressure at the inlet of the pressure control valve. The invention also relates to hydraulic systems, in which flow control valves of this type are arranged. The present invention relates, in particular, to hydrostatic profiled rail guides, in which flow control valves of this type are used.
The company Hydac International markets 2-way flow control valves according to DIN ISO 1219 for oil hydraulic systems, which 2-way flow control valves keep the emerging volumetric flow constant by a control operation. The volumetric flow is largely independent of the pressure and of the viscosity. The magnitude of the volumetric flow is defined by a fixed diaphragm (measuring diaphragm) and can be adjusted in a defined range. Said flow control valves are installed in oil hydraulic systems and are no longer accessible from the outside in the installed state. Unauthorized adjustment is accordingly not possible. Said flow control valves are distinguished by a compact design and space-saving installation in connecting housings, control blocks and, in particular, in the case of constricted installation conditions.
Flow control valves of this type are fixed diaphragm valves with differential pressure regulators which are connected downstream of them for oil hydraulic systems. The differential pressure regulator comprises substantially a control piston, a compression spring, a control diaphragm and the setting part, in particular the setting screw for setting the control pressure difference. The measuring diaphragm defines the volumetric flow setting range. A flow through the flow control valve from the inlet opening to the outlet opening brings about a pressure gradient at the measuring diaphragm. The differential pressure regulator moves into a control position which corresponds to the force equilibrium from the action of force of the pressure gradient across the measuring diaphragm multiplied by the control piston surface area on one side and the compression spring force on the other. As the throughflow rises, that is to say as the pressure gradient increases, the cross section of the control diaphragm is reduced in accordance with the increased pressure gradient until there is a force equilibrium again. A constant volumetric flow on the path of the hydraulic fluid from the inlet opening to the outlet opening is ensured by the continuous readjustment of the differential pressure regulator as a function of the prevailing pressure gradient. Flow can pass through the valve uncontrolled in the opposite direction.
If flow control valves of this type are used, for example, in hydrostatic profiled rail guides, in which a guide carriage is mounted hydrostatically on a guide rail, pressure pockets between the guide rail and the guide carriage are loaded with hydraulic fluid. Depending on the loading of the guide carriage, it can be required to adapt the control behavior of the differential pressure regulator. In the case of the known flow control valves which are described in the introduction, that would have the consequence in a profiled rail guide that said profiled rail guide first of all has to be decommissioned, the guide carriage then has to be opened to such an extent that there is access to the flow control valve, in order finally to set the setting screw for changing the control behavior of the differential pressure regulator to the given loading of the guide carriage. Following this setting work, the guide carriage has to be reassembled and the hydrostatic profiled rail guide has to be recommissioned. This procedure is complicated and, depending on the application of profiled rail guides of this type, can have the consequence of a temporary production downtime.